Some properties of lysosomal arylamidase in rat liver

Lysosomal arylamidase in rat liver was reassessed. The arylamidase was distinguishable into seven types having different isoelectric points by isoelectric fractionation. All the types hydrolyzed valine beta-naphthylamide most rapidly among amino acid beta-naphthylamides tested, but did not hydrolyze arginine beta-naphthylamide. These enzymes exhibited maximum activities at pH 7.0. They had a molecular weight of 135,000 by gel filtration on a Sephacryl S-200. They were all inhibited by sulfhydryl-blocking reagents and activated by sulfhydryl compounds, indicating to be cysteine proteases.